The present invention relates to the field of laminoplasty, and, more particularly, to laminoplasty devices and methods.
Every year there are a significant number of people who suffer severe neck, back, and/or spine injuries from trauma (see FIG. 1 for a perspective view of a typical human spine 100, including the cervical 110, thoracic 120, lumbar 130, sacrum 140, and coccyx 150 regions). These injuries include cervical fractures, fracture dislocations combined with retropulsion of the disc, and other major injuries. Also, each year many people undergo spine surgery for degenerative diseases, especially degenerative spinal stenosis. In spinal stenosis, the spinal canal, which contains and protects the spinal cord and nerve roots, narrows, which results in compression of the spinal cord and nerves. Surgical goals can include a decompression of all compressed levels of the spine and stabilization with solid fusion.
To provide further anatomical background, FIG. 2 is a perspective view, showing the structure of a typical vertebra 200. The exact structure of the vertebrae in each section of the spine may vary somewhat to accommodate the function required of that section. Nevertheless, the typical vertebra 200 includes an anterior portion called the spinal body 210 and a posterior portion called the vertebral arch 220 which surround the spinal canal 280. The vertebral arch 220 includes the spinous process 250, which is connected to the articular facet 230 and the transverse facet 260 by laminae 240. The facets 230, 260 are connected to the spinal body 210 by pedicles 270.
There are two posterior surgical methods for creating more room in the spinal canal. The first is a laminectomy in which the bony structures forming the back of the canal and the associated ligaments are removed. In the cervical region, a laminectomy can lead to spinal instability, or what is referred to as the “swan neck” deformity. This deformity can be a very difficult problem to correct and can cause substantial discomfort in the neck and shoulders due to the lack of the supporting structures at the back of the vertebrae which normally perform some of the work of keeping the neck in the right shape. It can also lead to further spinal cord damage.
An alternative way of relieving spinal cord pressure is a surgical procedure called a laminoplasty. Laminoplasty procedures concern altering one or more of the bony vertebral structures that surround and define the spinal canal. For example, the bony structures can been weakened and flexed or swung posteriorly to open the canal and provide additional room for the spinal cord. A problem associated with this procedure concerns stabilizing the altered one or more vertebrae for proper healing.
The laminoplasty technique is often referred to as an “open door laminoplasty,” because the back of one or more vertebrae is made to swing open like a door. There are multiple variations of the laminoplasty procedure, including the hemilateral open door laminoplasty (a.k.a., single door laminoplasty), and the bilateral open door laminoplasty (a.k.a., middorsal laminoplasty, French door laminoplasty, or double door laminoplasty).
For the hemilateral open door laminoplasty, one challenge is to securely maintain the separation between the posterior portion and the anterior portion of the divided lamina. Although it is known to use a bone graft to provide this separation, the use of such grafts can require additional surgery and time to harvest an appropriate piece of graft bone, typically from the pelvis of the patient or cadaver. Moreover, it is possible for the bone graft to move after the laminoplasty surgery. This potentially causes a narrowing of the cross-sectional area of the spinal canal, impingement on the patient's spinal cord, and/or disruption or prolongation of fusion.
With regard to the French door laminoplasty, the challenges can be even greater. For example, sutures have been used to secure a bone graft to the sectioned and separated laminae. Such sutures, however, are technically difficult, time consuming to insert, and typically do not firmly secure the bone graft to the sectioned laminae. Thus, subsequent movement between the bone graft and either of the two sectioned laminae can disadvantageously disrupt and/or prolong fusion therebetween.